Conventionally, a flowmeter has a detecting portion that detects a flow amount of fluid. The flowmeter includes a control circuit that electrically controls the detecting portion. The flowmeter has a sealing structure, in which the control circuit is accommodated in a casing member, and is embedded in a gelled material, thereby protecting the control circuit.
In this structure, the control circuit may cause disorder due to heat radiating from the control circuit. According to JP-A-6-160144, a radiation member is insert-molded in a resinous member, which serves as the casing member, so that heat of the control circuit is radiated to the outside of the casing member via the radiation member.
In this structure, a boundary, which is between the resinous member and the radiation member, has the periphery that connects with the sealing material in the casing member. The boundary has a gap due to thermal shrinkage caused in the insert molding. Therefore, the sealing material may leak to the outside of the casing member through the boundary, which is between the resinous member and the radiation member. In the above structure, the area of the boundary between the resinous member and the radiation member is set large, so that a path, through which the sealing material leaks, is set long. However, as long as the sealing material flows into the boundary between the resinous member and the radiation member through the periphery of the boundary, the sealing material cannot be sufficiently restricted from leaking. In addition, flow of liquid in the direction opposite to the leakage of the sealing material cannot be sufficiently restricted. For example, liquid such as water in the outside of the casing member cannot be sufficiently restricted from intruding into the casing member through the boundary between the resinous member and the radiation member.